If the aim of this rule is to reduce rotations then it ain't gunna work.

Lets say a team currently averages 140 rotations per game, or 35 per quarter divided by four players that works out to 8.75 rotations based on four players, spread amongst 18 players on the field. Based on 30 minute quarters and 8.75 rotations per qrt, this is an average of 3.43 minutes per rotation

Under the new rules if teams continue with 140 rotations and only have 3 on the bench then that means 11.67 rotations per each on the bench or an extra 3 per quarter or a rotation every 2.57 minutes.

Not much difference.